Effects of naloxone on pethidine-induced neonatal depression. Part I--Intravenous naloxone

Naloxone for opioid-exposed newborn infants

BACKGROUND

Naloxone, a specific opioid antagonist, is available for the treatment of newborn infants with cardiorespiratory or neurological depression that may be due to intrauterine exposure to opioid. It is unclear whether newborn infants may benefit from this therapy and whether naloxone has any harmful effects.

OBJECTIVES

To determine the effect of naloxone on the need for and duration of neonatal unit stay in infants of mothers who received opioid analgesia prior to delivery or of mothers who have used a prescribed or non-prescribed opioid during pregnancy.

SEARCH METHODS

We searched the following databases in February 2018: the Cochrane Central Register of Controlled Trials (the Cochrane Library 2018, Issue 1), MEDLINE (OvidSP), MEDLINE In process & Other Non-Indexed Citations (OvidSP), Embase (OvidSP), CINAHL (EBSCO), Maternity and Infant Care (OvidSP), and PubMed. We searched for ongoing and completed trials in the WHO International Clinical Trials Registry Platform and the EU Clinical Trials Register. We checked the reference lists of relevant articles to identify further potentially relevant studies.

SELECTION CRITERIA

Randomised controlled trials comparing the administration of naloxone versus placebo, or no drug, or another dose of naloxone to newborn infants with suspected or confirmed in utero exposure to opioid.

DATA COLLECTION AND ANALYSIS

We extracted data using the standard methods of Cochrane Neonatal with separate evaluation of trial quality and data extraction by two review authors and synthesis of data using risk ratio, risk difference, and mean difference.

MAIN RESULTS

We included nine trials, with 316 participants in total, that compared the effects of naloxone versus placebo or no drug in newborn infants exposed to maternal opioid analgesia prior to delivery. None of the included trials investigated infants born to mothers who had used a prescribed or non-prescribed opioid during pregnancy. None of these trials specifically recruited infants with cardiorespiratory or neurological depression. The main outcomes reported were measures of respiratory function in the first six hours after birth. There is some evidence that naloxone increases alveolar ventilation. The trials did not assess the effect on the primary outcomes of this review (admission to a neonatal unit and failure to establish breastfeeding).

AUTHORS' CONCLUSIONS

The existing evidence from randomised controlled trials is insufficient to determine whether naloxone confers any important benefits to newborn infants with cardiorespiratory or neurological depression that may be due to intrauterine exposure to opioid. Given concerns about the safety of naloxone in this context, it may be appropriate to limit its use to randomised controlled trials that aim to resolve these uncertainties.

Cardiorespiratory Effects of Naloxone in Children

BACKGROUND:

Data on the cardiorespiratory changes and complications following administration of naloxone in children are limited.

OBJECTIVE:

To evaluate the cardiorespiratory changes and complications following naloxone treatment in children.

METHODS:

The maximal changes in respiratory rate (RR), heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressure, and any complications within 1 and 2 hours following naloxone were tabulated.

RESULTS:

One hundred ninety-five children received naloxone over 3 years. The mean ± SD age was 9.7 ± 6 years. The total doses of naloxone ranged from 0.01 to 7 mg (0.001–0.5 mg/kg body weight), with a median dose of 0.1 mg. Group 1 patients consisted of 11 6 (60%) children who were postoperative and had been given naloxone by an anesthesiologist; group 2 patients consisted of 79 (40%) children who received naloxone in the emergency department or pediatric intensive care unit. Patients in group 1 were older: 10.6 ± 5.3 versus 8.2 ± 6.7 years (p < 0.006), but received significantly lower doses of naloxone (0.09 ± 0.2 vs. 1.1 ± 0.76 mg; p < 0.001). When the entire cohort was evaluated, a significant increase in RR (15 ± 7 vs. 21 ± 8 breaths/min; p < 0.001), HR (102 ± 29 vs.107 ± 29 beats/min; p < 0.001), SBP (109 ± 17 vs. 115 ± 15 mm Hg; p < 0.001), and DBP (56 ± 10 vs. 60 ± 13 mm Hg; p < 0.001) within 1 hour following naloxone was noted. When the 2 groups were compared, only the changes in RR were greater in group 2 patients (6.8 ± 7.9 vs. 4.7 ± 5 breaths/min; p < 0.001) following naloxone. Systolic hypertension occurred in 33 of 195 (16.9%) of all patients, while diastolic hypertension occurred in 13 (6.6%) of all patients after naloxone. Only the incidence of diastolic hypertension was higher in group 2 compared with group 1 patients following naloxone (16% vs. 2%; p < 0.001). Hypertension resolved spontaneously. One child developed pulmonary edema and required positive pressure ventilation for 22 hours.

CONCLUSIONS:

Moderate increases in RR, HR, and BP occur after naloxone administration to children, but development of more serious complications is rare.

Naloxone for opiate-exposed newborn infants

BACKGROUND

Naloxone, a specific opiate antagonist, is available for the treatment of newborn infants with cardiorespiratory or neurological depression that may be due to intrauterine exposure to opiate. It is unclear whether newborn infants may benefit from this therapy and whether naloxone has any harmful effects.

OBJECTIVES

To determine the effect of naloxone as a treatment for newborn infants who have been exposed in utero to opiate.

SEARCH METHODS

We searched the following databases in June 2012 for new studies published since the previous search in 2007: The Cochrane Central Register of Controlled Trials (The Cochrane Library 2012, Issue 6), MEDLINE (OvidSP), MEDLINE In process & Other Non-Indexed Citations (OvidSP), EMBASE (OvidSP), CINAHL (EBSCO), Maternity and Infant Care (OvidSP) and PubMed. We searched for ongoing and completed trials in Clinical Trials.gov, metaRegister of Controlled Trials, WHO International Clinical Trials Registry Platform and the EU Clinical Trials Register. We checked the reference lists of relevant articles to identify further potentially relevant studies.

SELECTION CRITERIA

Randomised controlled trials comparing the administration of naloxone versus placebo, or no drug, or another dose of naloxone to newborn infants with suspected or confirmed in utero exposure to opiate.

DATA COLLECTION AND ANALYSIS

We extracted data using the standard methods of the Cochrane Neonatal Review Group with separate evaluation of trial quality and data extraction by two review authors and synthesis of data using risk ratio, risk difference and weighted mean difference.

MAIN RESULTS

We included nine trials that compared the effects of naloxone versus placebo or no drug in newborn infants exposed to maternal opiate analgesia prior to delivery. None of these trials specifically recruited infants with cardiorespiratory or neurological depression. The main outcomes reported were measures of respiratory function in the first six hours of life. There is some evidence that naloxone increases alveolar ventilation. The trials did not assess the effect on the primary outcomes of this review (admission to a neonatal unit and failure to establish breastfeeding).

AUTHORS' CONCLUSIONS

The existing evidence from randomised controlled trials is insufficient to determine whether naloxone confers any important benefits to newborn infants with cardiorespiratory or neurological depression that may be due to intrauterine exposure to opiate. Given concerns about the safety of naloxone in this context it may be appropriate to limit its use to randomised controlled trials that aim resolve these uncertainties.

Prescribing intramuscular opioids for labour analgesia in consultant-led maternity units: a survey of UK practice

BACKGROUND

Intramuscular opioids are widely used for analgesia in labour. We conducted a postal survey to establish current prescribing and monitoring guidelines for intramuscular opioids in consultant-led obstetric units in the UK.

METHODS

A postal questionnaire was sent between December 2005 and January 2006 to the lead obstetric anaesthetist of all 234 consultant-led obstetric units in the UK. We enquired about dose regimens of intramuscular opioids in labour and monitoring of mother, fetus and neonate.

RESULTS

The response rate was 71%; 84.4% of responding units used pethidine and 34.1% diamorphine. Meptazinol and morphine were available in 13.8% and 13.2% of units respectively. Some units used more than one opioid. The choice of opioid was dictated mainly by tradition (65.3%) and familiarity (40.7%). Prophylactic antiemetics were co-administered in 73.7% of units, the most commonly used being prochlorperazine (30.5%). Vital signs were monitored in 91.6% of units: in total 10.2% measured haemoglobin oxygen saturations and 4.8% respiratory rate. Pain scores were recorded in 13.7% of units.

CONCLUSIONS

When compared with previous studies the use of intramuscular diamorphine is increasing in UK consultant-led obstetric units, although pethidine remains the widely used opioid. At present this change cannot be justified by a suitably powered, randomised study comparing intramuscular pethidine with diamorphine.

Safe reduction in administration of naloxone to newborn infants: an observational study

BACKGROUND

Naloxone, a specific opiate antagonist, is widely used during neonatal resuscitation to reverse possible opiate-induced respiratory depression.

AIM

To determine the frequency with which naloxone is administered when resuscitation guidelines are conscientiously followed and to document any effect on respiratory morbidity.

METHODS

Perinatal data including naloxone administration and respiratory morbidity were collected retrospectively, and compared with prospectively collected data following the introduction of "Good Practice" guidelines.

RESULTS

There were 500 deliveries in the retrospective arm of the study and 1000 deliveries in the prospective arm. Although a similar proportion of women received opiates in labour in the two periods of study, there was a marked reduction in the use of naloxone when the guidelines were introduced (11% of opiate-exposed deliveries compared to 0.2%). There was no significant effect on respiratory morbidity with the change in practice.

CONCLUSION

Naloxone is rarely needed to reverse the effects of opiates in newborn infants, and its use can be curtailed by following current resuscitation guidelines without increasing respiratory morbidity.

Naloxone during neonatal resuscitation: acknowledging the unknown

There are no studies to support or to refute the current recommendations regarding naloxone concentration, routes for administration, and doses in neonatal resuscitation in the delivery room. Given the lack of supporting evidence, naloxone should not be given routinely in the delivery room to depressed neonates whether or not they are exposed to opioids before delivery because no important improvement has been documented and the drug may have potential short- and long-term harmful effects.

Intragroup differences in risk factors for breastfeeding outcomes in a multicultural community

A sample of 221 women who delivered at Al Qassimi Hospital, Sharjah, United Arab Emirates, were included in this prospective study to identify breastfeeding patterns at day 1, 1 month, and 6 months postpartum. The exclusive breastfeeding rate was 76.5% on day 1, 48.4% at 1 month, and 13.3% at 6 months. At 6 months, 16.1% had stopped breastfeeding. Simple and multivariable binary logistic regression analyses were used to identify factors associated with better breastfeeding outcomes. Nationality significantly affected exclusive breastfeeding at day 1 and 1 month. Pethidine use was associated with lower levels of exclusive breastfeeding at 1 month. Education was the most significant determinant of breastfeeding behavior at 6 months. Effects of the interrelationships between factors were examined and shown to influence breastfeeding outcomes in different population subgroups. The findings of this study suggest that strategies to improve breastfeeding should focus on risk factors specific to the population subgroup.

Naloxone for narcotic exposed newborn infants: systematic review

BACKGROUND

Naloxone, a specific opiate antagonist, is available for the treatment of newborn infants with respiratory depression that may be due to transplacentally acquired opiates.

AIMS

To determine if this treatment has any clinically important benefits, and whether there are any harmful effects.

METHODS

Randomised controlled trials that compared naloxone with placebo or no drug for newborn infants with transplacental exposure to narcotics were systematically reviewed. The Cochrane Controlled Trials Register (CCTR; 2002, Issue 3), Medline (1966 to June 2002), and Embase (1988 to June 2002) were searched. Data were extracted, analysed, and synthesised using the standard methods of the Cochrane Neonatal Collaborative Review Group.

RESULTS

Nine trials were found that fulfilled the specified inclusion criteria. Although there was evidence that naloxone increased alveolar ventilation, no data were found on the specified primary outcomes of this review: the need for assisted ventilation or admission to a neonatal unit.

CONCLUSIONS

There is a need for a randomised controlled trial to determine if naloxone confers any clinically important benefits on newborn infants with respiratory depression that may be due to transplacentally acquired narcotic.

Naloxone for narcotic-exposed newborn infants

BACKGROUND

Naloxone, a specific opiate antagonist, is available for the management of newborn infants with respiratory depression that may be due to transplacentally-acquired opiates. However, it is unclear which groups of newborn infants may benefit from this therapy, and whether naloxone has any harmful effects.

OBJECTIVES

In newborn infants who have been exposed trans-placentally to narcotics, does naloxone reduce the need for, or duration of, ventilatory support or neonatal unit admission.

SEARCH STRATEGY

The standard search strategy of the Cochrane Neonatal Review Group was used. This included electronic searches of the Cochrane Controlled Trials Register (The Cochrane Library, Issue 1, 2002), MEDLINE (1966 - February 2002), EMBASE (1988 - February 2002), and previous reviews including cross references.

SELECTION CRITERIA

Randomised controlled trials comparing the administration of naloxone versus placebo, or no drug, or another dose of naloxone, to newborn infants with suspected or confirmed trans-placental exposure to narcotics.

DATA COLLECTION AND ANALYSIS

Data were extracted using the standard methods of the Cochrane Neonatal Review Group, with separate evaluation of trial quality and data extraction by each author and synthesis of data using relative risk, risk difference and weighted mean difference.

MAIN RESULTS

We found nine trials that compared the effects of naloxone versus placebo or no drug in newborn infants exposed to maternal narcotic analgesia prior to delivery. The main outcomes reported were measures of respiratory function in the first six hours of life. Although we found some evidence that naloxone increases alveolar ventilation, we did not find any data on the pre-specified primary outcomes of this review: the need for assisted mechanical ventilation or admission to a neonatal unit.

REVIEWER'S CONCLUSIONS

There is a need for a randomised controlled trial to determine if naloxone confers any clinically important benefits to newborn infants with respiratory depression that may be due to trans-placentally acquired narcotic.

Intramuscular opioids for maternal pain relief in labour: a randomised controlled trial comparing pethidine with diamorphine

OBJECTIVE

To compare the pain relief and side effects of intramuscular pethidine with intramuscular diamorphine in labour.

DESIGN

Double-blind randomised controlled trial.

SETTING

The labour ward in a UK teaching hospital.

PARTICIPANTS

Sixty-nine nulliparous women and 64 multiparous women in labour who requested narcotic analgesia and remained undelivered one hour after trial entry.

METHODS

Nulliparous women were randomised to receive either 150 mg intramuscular pethidine or 7.5 mg intramuscular diamorphine. Multiparous women were randomised to receive either 100 mg intramuscular pethidine or 5 mg intramuscular diamorphine. All participants received the anti-emetic prochloroperazine at the same time as the trial drugs.

MAIN OUTCOME MEASURES

Maternal analgesia assessed by a visual analogue score and verbal scales of pain intensity and pain relief, maternal sedation and vomiting, neonatal outcome assessed by Apgar scores and the need for resuscitation.

RESULTS

More women allocated to receiving pethidine than to diamorphine reported slight or no pain relief at 60 minutes after administration of these drugs (P = 0.03). This trend was repeated in most of the other measures for maternal analgesia. There was no difference in maternal sedation, but the incidence of vomiting within 60 minutes was lower for women who received diamorphine (P = 0.02). Pethidine was associated with lower Apgar scores at 1 minute (P < 0.05).

CONCLUSION

Intramuscular diamorphine in labour appears to have some benefits, compared with intramuscular pethidine, but the trial was small and further research, particularly into alternative opioids and long term effects on the infants is still needed.

Techniques to study human placental transport

Pregnancy in the 20th century involves women of many age groups from early teens to the fourth or fifth decade. Modern medicine and in vitro fertilization techniques have increased options for pregnancy and childbirth. Pregnancy is a dynamic state, and medical concerns may involve disorders of the fetus and mother requiring medications and special nutrients. Therefore, different techniques have been developed to evaluate the placental transfer of drugs and nutrients using tissues and cells derived from human placenta. These include (a) isolated tissues and cells to study placental transport, (b) primary and malignant trophoblast cell cultures and (c) biophysical methods for studying placental transport. Also, convenient study models have been developed to evaluate placental transfer of safe drugs in pregnant women. Some of the drugs studied by these techniques and models include (a) anesthetics and pain medications used during delivery, (b) antibiotics and anti-bacterials used to cure infections, (c) drugs abused by pregnant women and (d) nutrients required for proper fetal growth. Placental transfer and exchange mechanisms are complicated processes, and in vitro models reflect only partially the equilibria that exist among mother, placenta and fetus. The perfused cotyledon model is elegant and simple but gives only restricted information. Isolated placental tissues give useful information about the pharmacological effects of drugs. Metabolic studies using human placental models provide information on the metabolism of a drug during placental transfer and accumulation of the drug or its metabolite in the placenta or fetal circulation. Several studies on the transplacental passage of drugs exist but many questions regarding the transfer of drugs between the maternal and fetal circulations and clearance of drugs from fetal circulation have yet to be answered. This article reviews in vitro and in vivo methods for evaluation of transplacental transport of drugs and their current effectiveness to obtain clinically useful data.

Labor analgesia and infant brain development

A large percentage of newborns are exposed to pharmacological agents that affect the brain in connection with pain management during labor. The two most commonly used agents are meperidine, administered intravenously or intramuscularly, and bupivacaine, administered by the epidural route. Over the years, infant behavioral assessments have been used in the neonatal nursery to identify labor analgesia regimens with minimal impact on neonatal status. However, considerable controversy has centered on the general issue of possible harm to the neonate from use of analgesia and anesthesia in obstetrics. Due to limitations on experiments in the obstetric situation and a lack of suitable animal models, the broader issues concerning the effects of these agents on the developing brain and possible long-term consequences for infant adaptive functioning have received little attention. A series of studies has recently been completed using a rhesus monkey model for administration of labor analgesia under controlled experimental conditions and long-term behavioral evaluation of infants. Most of the assessments, including those of cognitive function, were not influenced by perinatal analgesia. However, these studies have confirmed the neonatal depressant effects of meperidine and have suggested that the course of behavioral maturation during certain periods of infancy is influenced by both meperidine and bupivacaine administration at birth. These effects could occur as a result of effects on vulnerable brain processes during a sensitive period, interference with programming of brain development by endogenous agents, or alteration in early experiences.

A comprehensive review of naloxone for the emergency physician

Naloxone has enjoyed long-standing success as a safe and effective opioid antagonist and has been invaluable in defining the role of endogenous opioid pathways in the response to pathological states such as sepsis and hypovolemia. We look forward to exciting research to further elucidate these pathways and to improve outcome by modulating the patient's physiological response to these stresses.

Factors affecting the maternal-fetal distribution of pethidine and bupivacaine in the rabbit

Twenty pregnant New Zealand white rabbits (mean body weight 4.6 kg) within 3 days of term were anaesthetized and given an intravenous infusion of bupivacaine 1.25 mg/ml with pethidine 1.25 mg/ml at a rate of 12 ml/h for 20 min, 6 ml/h for 60 min and 3 ml/h thereafter. In 10 of the does the solution also contained adrenaline 1.25 microg/ml. Up to 8 fetuses were removed at 15 min intervals from the start of the infusion and umbilical vein pH was measured, together with bupivacaine and pethidine concentrations, in fetal plasma, fetal brain and maternal plasma sampled synchronously. Mean umbilical vein pH fell with time with no significant difference between the groups. Maternal plasma concentrations of both drugs did not alter significantly during the experiment. Maternal clearance of bupivacaine was 85.6 ml/min and of pethidine was 249 ml/min. Despite the three-fold higher maternal plasma concentrations of bupivacaine, concentrations of pethidine in fetal plasma and brain were consistently higher than those of bupivacaine. Fetal plasma pethidine concentrations rose 0.276 microg x ml(-1)h(-1) and bupivacaine concentrations rose 0.184 microg x ml(-1)h(-1). The mean (+/-SD) maximum fetal: maternal plasma ratio for bupivacaine was 0.361+/-0.127 and for pethidine 1.78+/-0.81. The fetal brain:plasma ratio of pethidine was consistently higher than that of bupivacaine and did not change significantly with time, whereas that of bupivacaine fell significantly (P<0.05). Concentrations of bupivacaine and pethidine in fetal and maternal brain were consistently higher with adrenaline, although adrenaline had no significant effect on the concentrations in this or any compartment.

A comparative study of intramuscular ketorolac and pethidine in labour pain

A single dose block randomised double-blind study comparing intramuscular ketorolac, 50 mg of pethidine and 100 mg pethidine was carried out in multiparous women. Pain intensity and sedation effect were recorded at inclusion to the study, half hourly for the first 2 h, then hourly until 6 h after delivery. Maternal and neonatal side effects were noted including the Apgar scores and the baby's requirements for resuscitation. All three treatments are relatively ineffective in relieving labour pain. There was no difference in the analgesic efficacy between the two doses of pethidine but both doses of pethidine were statistically more effective compared with ketorolac. There was no difference in the retrospective assessment of the three groups or when comparison was made with the previous labour. A similar number of patients required further analgesia in each group. In all three groups, no adverse effect occurred in the mother or fetus. Maternal sedation and fetal depression were statistically less in the ketorolac group. Although ketorolac had inferior analgesic effect, its use was not associated with clinically significant sequelae and it showed a superior safety profile compared with either dose of pethidine. The study was not powerful enough to detect a difference between 50 mg and 100 mg of pethidine.

Treatment options for the relief of pain during childbirth

Despite its severity, the disposition of women towards pain during childbirth is influenced by many complex personal and cultural factors. Such influences may inspire a degree of stoicism towards labour pain which would be extraordinary in other painful circumstances. Nevertheless, the majority of women who deliver in a modern obstetric unit request some form of pharmacological pain relief. An important component of proper antenatal education, therefore, is to provide impartial information about the various analgesic alternatives which are available within each centre. Regimens of analgesia which depend on the systemic absorption of drugs (e.g., parenterally administered opioids; inhalational analgesia) are simple to administer but they have limited efficacy and are commonly associated with unpleasant central side effects. While some innovations in actual drug administration have been introduced, it is unlikely that any further major improvements will be feasible using the systemic approach to analgesia. Epidural analgesia has become established as the most effective and consistently reliable method of providing pain relief in labour. Recent advances have demonstrated that many of the adverse effects traditionally associated with epidural analgesia can be substantially reduced by administering local anaesthetics in smaller doses. It is becoming apparent that additional patient benefits are possible when epidural opioids are also used in combination with local anaesthetics. Techniques which allow the mother to exercise personal control over her epidural analgesia requirements are received more favourably and may help reduce the need for obstetric intervention.

Pethidine compared with meptazinol during labour. A prospective randomised double-blind study in 1100 patients

A randomised double-blind comparison of pethidine and meptazinol used as analgesics in labour was carried out in 1,100 consecutive women who would normally have received intramuscular pethidine. Pain assessments at 30-minute intervals were made independently by patients and midwives. Maternal and neonatal side effects were noted. The babies' requirements for resuscitation and weight changes in the first 5 days were studied. There was no difference in the analgesia provided by the two drugs; the pattern of side effects was similar, but the incidence of vomiting was greater following meptazinol administration. The babies in the two groups were similar with respect to resuscitation received, weight gains or losses and the incidence of clinical neonatal jaundice. The most striking findings were the poor quality of pain relief experienced by both groups following parenteral analgesics and the high incidence of side effects.

Effects of drugs and chemicals on the fetus and newborn (1)

Drug teratogenicity has been demonstrated experimentally for more than 30 years. After the discovery of the thalidomide-induced embryopathies, the fetal dangers of maternal drug ingestion were overemphasized. Accumulation of additional information during the past 15 years has led to a more balanced viewpoint concerning drug teratogenicity. A complex set of circumstances must prevail for a specific teratogenic effect to result. Not only the drug or environmental pollutant in question but also its dose, timing, and frequency of administration as well as the genetic and individual susceptibility of the embryo are important factors. Herein we review the currently available information on drug and environmental effects on the fetus and neonate.

Naloxone protein binding in adult and foetal plasma

Binding of naloxone hydrochloride was determined at 37 degrees C, by equilibrium dialysis against 0.067 M phosphate buffer, pH 7.4, in plasma obtained from 18 healthy adults, and 18 samples of umbilical cord venous (foetal) plasma. The percentage free fraction (% free) in plasma was independent of naloxone concentration (9 ng/ml to 2.5 micrograms/ml). Percent free naloxone in adult (means = 54.0) was lower (p less than 0.01) than in foetal (means = 61.5) plasma. In buffered solutions of purified HSA, %free naloxone (means = 68.7) was independent of HSA concentration over the range 3.0 g/dl to 5.5 g/dl. Adult plasma concentrations of alpha 1-acid glycoprotein (alpha 1-AGP) and beta-lipoprotein were higher (p less than 0.01) than foetal concentrations. Furthermore %free naloxone in foetal plasma decreased with the in-vitro addition of purified alpha 1-AGP. It is suggested that qualitative differences in adult and foetal albumin and quantitative differences in plasma levels of alpha 1-AGP and perhaps beta-lipoprotein are responsible for naloxone plasma binding differences between adults and the newborn.

Determination of naloxone in blood by high-performance liquid chromatography

A rapid, sensitive, selective and reproducible reversed-phase high-performance liquid chromatographic method is described for the quantification of naloxone in small blood samples of premature infants. Naloxone and the internal standard, naltrexone, are extracted from alkalinized blood into diethyl ether and subsequently back extracted into 0.05% (v/v) phosphoric acid before chromatographing on a reversed-phase system. The mobile phase comprises 85 parts of acetonitrile and 15 parts of 0.06% (v/v) triethylamine in an aqueous phosphoric acid solution at pH 5 and is pumped at 1.5 ml/min. The retention times of naloxone and naltrexone were observed to be 5.4 and 7.5 min respectively. Ultraviolet detection at 214 nm enabled a limit of detection of 1 ng to be achieved. The reproducibility of the method was good at both 100 ng (C.V. = 3.4%; n = 9) and 10 ng (C.V. = 5.1%; n = 6). The high sensitivity and speed with which this assay can be performed makes it especially useful for the estimation of naloxone in small volumes (0.3-0.6 ml) of blood. It is thus particularly valuable for the determination of naloxone blood concentration-time profiles in premature infants where the minimization of the volume of blood collected is of paramount importance.

Opiates, endorphins and the developing organism: a comprehensive bibliography

A comprehensive bibliography of the literature concerned with opiates, endorphins, and the developing organism is presented. A total of 1378 clinical and laboratory references, with citations beginning in 1875, are recorded. A series of indexed accompanies the citations in order to make the literature more accessible. These indexes are divided into clinical and laboratory topics. The clinical section is subdivided into: age of subject examined; maternal aspects; effects on the fetus; pharmacology, physiology, and the withdrawal syndrome; and "other" effects on the offspring. The laboratory section is subdivided into: type of opiate/endorphin studied; species utilized; and major subject areas explored.

Maternal kinetics and transplacental passage of pethidine during labour

1 Pethidine is commonly used in single doses as an analgesic in obstetrics. Plasma concentration-time profiles of pethidine after intramuscular administration of 1.5 mg/kg body weight to 16 pregnant women during labour were investigated. There was only a two-fold variation in peak plasma concentration (300-650 ng/ml). The mean (+/- s.d.) value of the apparent plasma half-life of pethidine was 3.4 (+/- 1.0) h which is not different from that in healthy controls. norpethidine plasma levels were not measurable (less than 10 ng/ml). 2 The placental transfer transfer of pethidine was studied at delivery in samples from the umbilical cord vessels and from a maternal peripheral vein. In another 14 patients serial determinations of pethidine concentration were made in foetal scalp blood and maternal venous blood simultaneously during the different stages of labour. The foeto-maternal drug ratio varied between 0.35 and 1.5 with a positive correlation between ratio and dose delivery time interval. The concentration of pethidine in umbilical cord plasma or blood varied between 60 and 400 ng/ml with dose-delivery time intervals of 30 min to 10.5 h. The foetal concentration of pethidine reached a peak-plateau value between 1-5 h after dose.

Neonatal emergency transport drug box

The neonatal drug transport box provides a readily available drug supply in appropriate dilutions for newborns. It also supplies a visible neonatal emergency drug dosage list. The use of this box has demonstrated a saving in nursing time, assured an appropriate supply of all necessary drugs, made drugs readily available for emergency use, and provided dosage check.

Naloxone pharmacokinetics in the newborn

1 Plasma naloxone levels were determined by RIA over a period of 6--36 h in three groups of neonates, (1) those given 35 microgram i.v. (n = 6), (2) those given 70 microgram i.v. (n = 6) and (3) those given 200 microgram i.m. (n = 17) naloxone HCl within 1 min of birth. 2 After intravenous administration of 35 and 70 microgram of naloxone peak levels of 4--15 ng/ml and 9--20 ng/ml respectively were reached in 5--40 min and the mean plasma half-life after both doses was 3.1 +/- 0.5 h. 3 Peak levels of 7--35 ng/ml were reached 0.5 to 2 h after intramuscular administration of 200 microgram. The fall in concentration after this was consistently biphasic with the levels declining rapidly between one and four hours and then slowly from four hours onwards. 4 Plasma levels at 24--36 h after i.m. administration were as high as they were 4 h after i.v. administration of 35 microgram and this may account for the prolonged duration of action when this route is used.

Neonatal respiration, feeding and neurobehavioural state. Effects of intrapartum bupivacaine, pethidine and pethidine reversed by naloxone

The effects on mature newborn have been compared at 0.5, 4, 8 12 24 and 48 hr after birth, of maternally administered epidural bupivacaine (11 babies) or pethidine (18 babies) or pethidine reversed by naloxone administered intramuscularly to the newborn (15 babies). Bupivacaine (mean dose 130 mg) had less effect that pethidine (mean dose 183.3 mg) on alveolar carbon dioxide tension (PACO2) at 0.5 hr after birth, but had a similar effect to pethidine on feeding, elicited reflexes and produced more depression of muscle tone up to 48 hr. Bupivacaine had more effect on PACO2 feeding measures, elicited reflexes and muscle tone at almost all examination periods than pethidine (mean dose 157.0 mg) reversed by naloxone (200 micrograms intramuscularly). Except at delivery, the effects of bupivacaine or pethidine on respiration and feeding up to 48 hr after birth were similar. There were more signs of depression with both drugs than when pethidine had been reversed by naloxone.

Effects of pethidine and its antagonists on the newborn

Nalorphine and naloxone were compared as to their effectiveness as pethidine antagonists. 85 infants were divided into a control group containing 19 newborn babies whose mothers did not receive pethidine and the babies received no antagonist, and three groups in which the mothers all received pethidine and the babies had either no antagonist (24), nalorphine IV (16), or naloxone IV (26). All the babies were assessed by measuring their neurobehavioural states and respiratory functions. A further 12 newborn babies had naloxone plasma levels measured by radioimmunoassay. Although standard doses of nalorphine effectively antagonised the depressive effect on respiration induced by pethidine, there was a pronounced and undesirable excitatory agonist action. Naloxone was not observed to have any agonist activity, but the recommended IV dose (0.01 mg/kg) had only a slight and delayed antagonist action as measured by respiratory function tests. A more rapid and improved antagonism was noted after this dose was doubled (0.02 mg/kg). The plasma elimination-phase half-life of naloxone after intravenous cord injection was about 3 hours.20